e.s.a.d. stands for eat shit and die. its a good nickname someone that is really pissing you off because most people can not figure out what it means and if they do figure it out they will feel that there definition is right because they will feel like why would you call someone eat shit and die.

"okay e.s.a.d."
"what does that mean?"
"nothing it's just my new nickname for you"
"okey"